Solving Nonlinear Systems of Equations Via Spectral Residual Methods: Stepsize Selection and Applications

Spectral residual methods are derivative-free and low-cost per iteration procedures for solving nonlinear systems of equations. They are generally coupled with a nonmonotone linesearch strategy and compare well with Newton-based methods for large nonlinear systems and sequences of nonlinear systems. The residual vector is used as the search direction and choosing the steplength has a crucial impact on the performance. In this work we address both theoretically and experimentally the steplength selection and provide results on a real application such as a rolling contact problem

Simulation of the laser-plasma acceleration for the PLASMONX project with the PIC code ALaDyn

In this paper we will briefly introduce laser–plasma acceleration for electrons and present some numerical simulations. The simulations have been performed to find a suitable working point for one of the test experiments of the INFN–CNR PLASMONX project. FLAME (Frascati laser for acceleration and multidisciplinary experiments), a 300 TW Ti:Sa laser, is being installed and commissioned at Laboratori Nazionali di Frascati (LFN). The first pilot experiment SITE (self-injection test experiment) is planned for this year (2010). The simulations have been run using a fully self-consistent particle-in-cell code AlaDyn (Acceleration by LAser and DYNamics of charged particles) developed and maintained at the Department of Physics at the University of Bologna within the PLAMSONX project

Polarization Dependence of Bulk Ion Acceleration from Ultrathin Foils Irradiated by High-Intensity Ultrashort Laser Pulses

The acceleration of ions from ultrathin (10-100 nm) carbon foils has been investigated using intense (∼ 6 x1020 Wcm-2), ultrashort (45 fs) laser pulses, highlighting a strong dependence of the ion beam parameters on the laser polarization, with circularly polarized (CP) pulses producing the highest energies for both protons and carbons (25-30 MeV/nucleon); carbon ion energies obtained employing CP pulses were signicantly higher (∼2.5 times) than for irradiations employing linearly polarized (LP) pulses. Particle-in-cell simulations indicate that Radiation Pressure Acceleration becomes the dominant mechanism for the thinnest targets and CP pulses

Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets

The interaction of laser pulses with thin grating targets, having a periodic groove at the irradiated surface, has been experimentally investigated. Ultrahigh contrast ($\sim 10^{12}$) pulses allowed to demonstrate an enhanced laser-target coupling for the first time in the relativistic regime of ultra-high intensity >10^{19} \mbox{W/cm}^{2}. A maximum increase by a factor of 2.5 of the cut-off energy of protons produced by Target Normal Sheath Acceleration has been observed with respect to plane targets, around the incidence angle expected for resonant excitation of surface waves. A significant enhancement is also observed for small angles of incidence, out of resonance.Comment: 5 pages, 5 figures, 2nd version implements final correction

Evaluation of tsunamigenic hazard through numerical modeling from seismic and non-seismic sources in the Crotone offshore (Calabria, Southern Italy)

Tsunamis in the Mediterranean Sea can be considered among the major sources of hazard, both for the extension of the area that can be involved by the water impact and for the closeness of potential sources to the coast, which reduces dramatically the alert and evacuation time. Moreover, landslides, as other non-seismic tsunami sources, are often characterized by a lack of precursors (such as seismic shaking), a reason for which the ensuing waves are sometimes called “surprise tsunamis”

The FORUM end-to-end simulator project: architecture and results

FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) will fly as the ninth ESA's Earth Explorer mission, and an end-to-end simulator (E2ES) has been developed as a support tool for the mission selection process and the subsequent development phases. The current status of the FORUM E2ES project is presented together with the characterization of the capabilities of a full physics retrieval code applied to FORUM data. We show how the instrument characteristics and the observed scene conditions impact on the spectrum measured by the instrument, accounting for the main sources of error related to the entire acquisition process, and the consequences on the retrieval algorithm. Both homogeneous and heterogeneous case studies are simulated in clear and cloudy conditions, validating the E2ES against appropriate well-established correlative codes. The performed tests show that the performance of the retrieval algorithm is compliant with the project requirements both in clear and cloudy conditions. The far-infrared (FIR) part of the FORUM spectrum is shown to be sensitive to surface emissivity, in dry atmospheric conditions, and to cirrus clouds, resulting in improved performance of the retrieval algorithm in these conditions. The retrieval errors increase with increasing the scene heterogeneity, both in terms of surface characteristics and in terms of fractional cloud cover of the scene

Extensive study of electron acceleration by relativistic surface plasmons

The excitation of surface plasmons with ultra-intense (I ∼ 5 × 1019W/cm2), high contrast (∼1012) laser pulses on periodically modulated solid targets has been recently demonstrated to produce collimated bunches of energetic electrons along the target surface [Fedeli et al., Phys. Rev. Lett. 116, 015001 (2016)]. Here, we report an extensive experimental and numerical study aimed to a complete characterization of the acceleration mechanism, demonstrating its robustness and promising characteristics for an electron source. By comparing different grating structures, we identify the relevant parameters to optimize the acceleration and obtain bunches of ∼650 pC of charge at several MeV of energy with blazed gratings

High order integration schemes for particle in cell (PIC)

High order integration schemes to solve the Maxwell's equations for the fields and Newton's equations for the particles are presented

Radiation pressure acceleration: perspectives and limits

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Advances in target normal sheath acceleration theory

A theoretical model of the Target Normal Sheath Acceleration (TNSA) process, able to go beyond the limits of available descriptions, is developed. It allows to achieve a more satisfactory interpretation of TNSA. The theory, also supported by two dimensional particle-in-cell simulations, elucidates the role played by the main laser and target parameters. Comparison between model predictions and experimental data related to the target thickness dependence of the maximum ion energy is discussed, showing satisfactory agreement. The model can be used as a simple but effective tool to guide the design of future experiments